An infusion speed measurement instrument 1 includes: a housing 12 which includes a fitting recessed part 10 in which a side wall 2a of a drip chamber 2 hung in an up-down direction is detachably fitted and a positioning contact part 11 which is in contact with a lower surface 23a of a flange part 23 of the drip chamber 2 fitted in the fitting recessed part 10 an infusion fluid detector 13 which is provided in the housing 12 and is configured to detect infusion fluid 4 dropping from a pipe 32 of the drip chamber 2 which is fitted in the fitting recessed part 10 while being in contact with the positioning contact part 11 at the flange part 23.
